This invention relates generally to dental appliances and more particularly to dental posts and devices used to handle dental posts.
It is well known in the field of dentistry to build up a dental restoration onto a tooth stub for replacement of missing dentition. The diseased or broken tooth is prepared leaving a tooth stub that provides a suitable support on which the restoration will be placed. After the root canal is cleaned and filled with the appropriate filling material it is partially reamed out to a proper size and depth forming a bore. A dental post is then selected and inserted into the prepared bore so that its shank substantially fills the bore while its head portion extends upwardly from the surface of the tooth stub. The post is retained within the bore using a suitable dental cement. Next, using a syringe or other dispensing means, a flowable dental core material is injected over the post head. The core material is formed and allowed to cure and harden on the post head to form a post-core buildup. Then, using a drill equipped with a high speed diamond burr, the post-core buildup is shaped to be fitted under a dental restoration, e.g., a porcelain or gold crown. Next, an impression is taken of the shaped post-core buildup which is used to fabricate the dental restoration. Finally, the dental restoration is fitted over the post-core buildup and cemented in place.
While numerous types of dental posts have provided improvements with respect to retention to and integration with core material, still further improvements would be beneficial so as to prevent accidental breaking off of the dental restoration after setting onto the dental post.
Some of the prior art posts utilized for such dental restorations contain enlarged heads or heads featuring indentations or dimples into which core material can flow. The difficulty with these prior art post designs is that because the indentations are not through openings, core material cannot flow deeply into the head portion and therefore cannot integrate as effectively with the post. By providing through openings in the post head in the present invention, a more effective integration between post head and core material will occur resulting in a stronger post-core buildup.
By way of example, U.S. Pat. Nos. 5,094,618 (Sullivan) and 5,073,112 (Weil) both show a dental post comprising a head portion featuring a pair of spheres with elongated indentations triangularly positioned thereon. Although such indentations may aid in providing some degree of retention between the dental post and core material, there is nothing set forth in either Sullivan or in Weil to suggest or indicate that the indentations are through openings that would permit core material to flow therethrough to facilitate a high degree of integration with the head portion of the dental post. Because the indentations are not through openings, the posts described therein appear to be unable to achieve an optimal degree of integration.
U.S. Pat. No. 4,752,225 (Bori) discloses a dental post having plural concave dimples on the surface of its head portion. According to Bori, the concave dimples help to hold a crown thereon by cement solidifying in the concave dimples. However, it appears that Bori does not show these dimples as through holes that would permit flow of core material through to the interior of the head section of the dental post so as to integrate the head portion with the core material. Further, it appears Bori does not disclose a head portion featuring a coronal opening (i.e., an opening in the top of the post head) which allows for the flow of an increased amount of core material to the interior of the head portion. Because Bori does not describe or show a coronal opening or a coronal rest seat it appears incapable of achieving a very high degree of post-core integration.
U.S. Pat. No. 4,622,012 (Smoler) discloses a dental post system that features an inner post which is inserted into an outer post that has been previously inserted into a prepared canal. The inner post has a flattened head portion that features a plurality of cutouts through which core material permeates to secure anchorage with the inner post head. The patent illustrates a number of different embodiments of the inner post head portion which in all cases is flattened with cut-outs provided thereon. Although these cutouts may provide some amount of integration of core material by allowing the material to flow through the cut-outs, because the head portion is flattened or thin, it appears to lack volume and therefore only a small amount of core material actually enters within the head portion for integration therein. Additionally, Smoler does not disclose a coronal opening which allows for an additional amount of core material to integrate within the post head.
U.S. Pat. No. 4,600,392 (Weissman) discloses a contoured dental post for retaining dental restorations onto a prepared tooth stub. In one embodiment, the dental post includes a transverse opening that extends through the upper end of the dental post. However, the dental post disclosed therein does not feature a coronal opening or a bulbous head portion containing a hollow volume that allows core material to flow therein and integrate with the bulbous head.
U.S. Pat. No. 4,778,388 (Sadayuki and Takashi) discloses a dental post comprising a shank that is insertable in a treated root canal and a head portion that extends above the tooth root. In one embodiment, the dental post is comprised of a cylindrical head portion featuring recesses and an axial bore extending through the head portion and shank of the dental post. Although these recesses may provide some amount of integration of core material by allowing the material to flow therein, there is nothing to suggest that these recesses are passageways that communicate with the axial bore to form an internal volume into which core material can flow to integrate with the dental post. These passageways appear to be present for gripping purposes for removing the dental post from the root canal. Further, none of the embodiments show a bulbous head.
U.S. Pat. 4,846,685 (Martin) discloses an embodiment of a dental post having a shank containing plural through bore holes arranged radially along the surface of the shank and a bore hole running along the central axis of the shank. The axial bore hole communicates with the radial bore holes so that as cement flows therein it locks the post from within and without into the tooth root and also acts as an anti-rotational device giving increased retention. The purpose of these bore holes is for the passage of cement therethrough in order to lock the post into the root canal. The structure in Martin does not appear to show the use of radial and axial bore holes in the post head for the purpose of passage of core material therethrough to integrate with the dental post. Additionally, the structure shown in Martin is cylindrical and is not comprised of a bulbous head.
In addition, many of the prior art dental posts utilize spiral threads, segments or lands located over the outer surface of the shank portion that cut into and deform the dentin of the tooth root upon insertion in order to achieve retention within the root canal. On many of these prior art dental posts, the threads or lands exert outward expansive forces to the tooth root and at times cause the same to fracture. Therefore, it is important to prevent the fracture of the tooth root during the insertion of the shank portion of a dental post thereinto, and even during the subsequent use of the tooth after the dental post and crown have been assembled to the root.
Therefore, the foregoing prior art dental posts, for reasons previously discussed, suffer from one or more drawbacks including poor integration with dental core material, poor adhesion to dental cement, risk of tooth root fracture during insertion of the post shank and high fabrication and installation costs.